Re: [PATCH] barrier patch set

[Jeff Garzik]

Chris Mason wrote:
> On Wed, 2004-03-31 at 09:08, Stephen C. Tweedie wrote:
>
> > Hi,
> >
> > On Tue, 2004-03-30 at 23:21, Jeff Garzik wrote:
> >
> >
> > > For IDE, O_DIRECT and O_SYNC can use special "FUA" commands, which don't 
> > > return until the data is on the platter.
> >
> > fsync() is still really nasty, because that can require that we wait on
> > IO that was submitted by the VM before we knew that there was a
> > synchronous IO wait coming.  
>
>
> Yes, it gets ugly in a hurry.  Jeff, look at the whole thread about the
> O_DIRECT read vs buffered write races.  I don't think we can use FUA for

Yes, I'm aware of the thread...


> fsync or O_SYNC without using it for every write.

Why not for O_SYNC?  Is some crazy userspace application flipping this 
bit on and off rapidly?


> We might be able to get away with using it on O_DIRECT.

Nod.

	Jeff



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